If this is Ballistic Gel; The 12" mark speaks for it self. The rest is dimensional, relative to tissue disruption. Whether or not clothing, plywood, glass etc.... has been put in front of the "Gel" is UNK.
Regarding, Tissue disruption this displays a facsmile of both permanent
and temporary tissue cavity or disruption the bullet causes. There is a huge discussion of the effect between temporary and permanent tissue disruption.
Catfish88 Should weigh in on this !